The present invention relates generally to medical methods and devices, and more particularly to thrombolectomy catheters, and methods for using such catheters, for removing blood clots or other matter from the lumens of blood vessels or other anatomical conduits.
Various types of thromboembolic disorders, such as stroke, pulmonary embolism, peripheral thrombosis, atherosclerosis, and the like, are known to occur in human beings and other mammals. Such thromboembolic disorders are typically characterized by the presence of a thromboembolus (i.e., a viscoelastic blood clot comprised of platelets, fibrinogen and other clotting proteins) which has become lodged at a specific location in a blood vessel.
In cases where the thromboembolism is located in a vein, the obstruction created by the thromboembolus may give rise to a condition of blood stasis, with the development of a condition known as thrombophlebitis within the vein. Moreover, peripheral venous embolisms may migrate to other areas of the body where even more serious untoward effects can result. For example, the majority of pulmonary embolisms are caused by emboli that originate in the peripheral venous system, and which subsequently migrate through the venous vasculature and become lodged with the lung.
In cases where the thromboembolus is located within an artery, the normal flow of arterial blood may be blocked or disrupted, and tissue ischemia (lack of available oxygen and nutrients required by the tissue) may develop. In such cases, if the thromboembolism is not relieved, the ischemic tissue may become infarcted (i.e., necrotic). Depending on the type and location of the arterial thromboembolus, such tissue infarction can result in death and amputation of a limb, myocardial infarction, or stroke. Notably, strokes caused by thromboemboli which become lodged in the small blood vessels of the brain continue to be a leading cause of death and disability, throughout the world.
In modern medical practice, thromboembolic disorders are typically treated by one or more of the following treatment modalities:
a) pharmacologic treatment wherein thrombolytic agents (e.g., streptokinase, urokinase, tissue plasminogen activator (TPA)) and/or anticoagulant drugs (e.g., heparin, warfarin) are administered in an effort to dissolve and prevent further growth of the clot;
b) open surgical procedures (e.g., surgical embolectomy or clot removal) wherein an incision is made in the blood vessel in which the clot is lodged and the clot is removed through such incision-sometimes with the aid of a balloon-tipped catheter (e.g., a xe2x80x9cFogarty Catheterxe2x80x9d) which is passed through the incision and into the lumen of the blood vessel where its balloon is inflated and used to extract the clot out of the incision; and,
c) transluminal catheter-based interventional procedures wherein a clot removing/disrupting catheter (e.g., a suction-type catheter having a suction tip, clot-capturing type catheter having a clot capturing receptacle (e.g., a basket, coil, hook, etc.), or clot-disrupting catheter having a clot disrupting apparatus (e.g., an ultrasound probe or laser)) is percutaneously inserted and advanced through the patient""s vasculature to a location adjacent the clot. The suction tip, clot capturing receptacle or clot disrupting apparatus is used to aspirate, capture and remove, disrupt or ablate the offending clot.
Each of the above-listed treatment modalities has its own set of advantages and disadvantages. For example, pharmacologic treatment has the advantage of being non-invasive and is often effective in lysing or dissolving the clot. However, the thrombolytic and/or anticoagulant drugs used in these pharmacologic treatments can cause untoward side effects such as bleeding or hemorrhage. Also, in cases where time is of the essence, such as cases where an arterial thromboembolism is causing severe tissue ischemia (e.g., an evolving stroke or an evolving myocardial infarction) the time which may be required for the thrombolytic drugs to fully lyse or dissolve the blood clot and restore arterial blood flow may be too long to avoid or minimize the impending infarction.
Open surgical thrombus-removing procedures can, in many cases, be used to rapidly remove clots from the lumens of blood vessels, but such open surgical procedures are notoriously invasive, often require general anesthesia, and the use of such open surgical procedures is generally limited to blood vessels which are located in surgically accessible areas of the body. For example, many patients suffer strokes due to the lodging of blood clots in small arteries located in surgically inaccessible areas of their brains and, thus, are not candidates for open surgical treatment.
Transluminal, catheter-based interventional procedures are minimally invasive, can often be performed without general anesthesia, and can in some cases be used to rapidly remove a clot from the lumen of a blood vessel. However, such catheter-based interventional procedures are highly operator-skill-dependent, and can be difficult or impossible to perform in small or tortuous blood vessels. Thus, patients who suffer strokes due to the presence of clots in the small, tortuous arteries of their brains may not presently be candidates for catheter-based, transluminal removal of the clot, due to the small size and tortuosity of the arteries in which their clots are located.
In concept, the transluminally deployable clot capturing type of catheters could be useable in ischemic strokes, because they are typically capable of removing an offending blood clot without the need for suction or application of energy (e.g., laser, ultrasound) which could be injurious to the delicate, small blood vessels of the brain. However, none of the prior art transluminally deployable clot capturing type of catheters are believed to be of optimal design for use in the small blood vessels of the brain because they are a) not equipped with appropriate guidewire passage lumens to allow them to be passed over previously inserted, small-diameter (e.g., 0.006-0.018 inch) guidewires, b) they are not adapted for rapid exchange over a guidewire of standard length (e.g., a guidewire which is less than twice the length of the catheter) and c) the clot capturing receptacles of these catheters are not optimally constructed and configured for removal of clots from very small blood vessels as are typically found in the brain.
Examples of transluminally deployable clot-capturing type embolectomy catheters of the prior art include those described in U.S. Pat. Nos. 4,706,671 (Weinrib), U.S. Pat. No. 4,873,978 (Ginsburg), U.S. Pat. No. 5,011,488 (Ginsburg), and U.S. Pat. No. 5,895,398 (Wensel, et al.). The ""390 patent to Wetzel, et al., discloses a clot capture device where a small catheter is first passed in a distal direction through a viscoelastic clot. A clot capture coil mounted to a stiff insertion mandrel is then advanced through the catheter and deployed on the distal side of the clot. The clot capture coil may be a plurality of wires having shape memory which radially expand into a variety of shapes that, when the insertion mandrel is retracted, ensnare the clot for removal. Despite extensive development in this area, for the reasons stated above and/or other reasons, none of the prior art embolectomy catheters are believed to be optimally designed for treating ischemic stroke.
Thus, there exists a need for the development of a new transluminally insertable, clot-pturing type embolectomy catheters which are advanceable and exchangeable over pre-inserted small diameter guidewires, and which are constructed to rapidly and selectively remove blood clots or other matter from small, delicate blood vessels of the brain, so as to provide an effective treatment for evolving strokes and other thromboembolic disorders.
The present invention generally comprises an embolectomy catheter device and method for removing blood clots or other matter from the lumens of blood vessels or other anatomical conduits of a mammalian body. The embolectomy catheters and methods of the present invention are particularly suitable for use in removing clots or thromboemboli from small arteries of the mammalian brain to prevent or minimize the severity of stroke.
A. Embolectomy Catheters of the Present Invention
In one aspect of the present invention, an embolectomy catheter for removing a blood clot or other such obstructive matter from a blood vessel is provided. The embolectomy catheter includes an elongate flexible catheter body having a proximal end, a distal end, an inner tube, and a guidewire lumen a part of which extends longitudinally through the inner tube. A clot removal device on the inner tube is deployable in a first state to a radially expanded configuration. A guidewire is sized to passed through the inner tube and project distally from the distal end of catheter body.
The catheter desirably includes an outer tube arranged to surround and constrain the clot removal device about the inner tube in a second state prior to its deployment to the first state. Both the catheter body and the clot removal device are passable through the clot in the second state. The catheter also may include a handle whereby an insertion portion of the catheter body extends distally from handle. The insertion portion includes the inner tube and outer tube, both extending substantially to the distal end of the catheter body. The inner and outer tubes are preferably relatively axially displaceable to cause the clot removal device to transition between the first and second state.
In a preferred embodiment, the clot removal device has a proximal end and a distal end, the distal end being attached to the inner tube and the proximal end being free to slide axially over the inner tube. The proximal end of the clot removal device is axially displaced away from the distal end within the outer tube so as to longitudinally stretch and radially constrain the device in the second state prior to its deployment to the first state. The clot removal device may take a variety of forms, but is preferably a plurality of separate wires attached at their distal ends to the inner tube and helically wound or looped about the inner tube at their proximal ends. In the first, deployed state, the plurality of helically wound wires radially expands into a tangled nest which is suitable for capturing the clot. Desirably, a marker band is arranged to slide longitudinally with the proximal end of clot removal device to indicate to operator the deployment state. Marker bands on both the inner and outer tubes provide further relative position indications.
In accordance with a further aspect of the invention, an embolectomy catheter for removing a blood clot or other such obstructive matter from a blood vessel comprises an elongate flexible catheter body having a proximal end, a distal end, an axis extending from a proximal end to the distal end, an inner tube, and an outer tube terminating just short of a distal end of catheter body. The clot removal device on the inner tube is initially collapsed and constrained in its collapse configuration by a portion of the outer tube. A distal tip of the catheter body located on the inner tube is adapted to pass through the blood clot to be removed. The outer tube is axially retractable to remove the constraint on the clot removal device such that it may radially expand to a deployed configuration.
Preferably, the outer tube extends distally within a proximal mouth of the distal tip prior to being retracted. The inner tube may be reinforced along its entire length, and is preferably more flexible at its distal end than at its proximal end. In addition, both the inner and outer tubes may include discrete segments that become more flexible in a direction from the proximal end to the distal end. In one embodiment, the catheter body has a size of between approximately 1-5 French at its distal end, and is preferably about 3 French.
A further aspect of present invention includes a handle attached to a proximal end of an insertion portion of catheter body. An actuator is provided on handle for proximally displacing the outer tube with respect to the inner tube in order to deploy the clot removal device. In one embodiment, the actuator comprises a slide movable along the handle and attached to the outer tube, the slide including a through bore for receiving an extension of the inner tube. An infusion port on the slide enables infusion of fluid in the annular space between the inner and outer tubes.
A further embolectomy catheter device of the present invention generally comprises; a) an elongate, pliable clot penetrating catheter which is advanceable, distal end first, through the clot or other obstructive matter (e.g., thrombus, thromboembolus, pieces of detached atherosclerotic plaque, foreign matter, etc.) which is to be removed, and b) a matter capturing receptacle which is deployable from the distal end of the catheter after it has been advanced through the obstructive matter, to capture and facilitate removal of the obstructive matter. The matter capturing receptacle is initially disposed in a first or stowed configuration wherein the receptacle is in a radially collapsed condition and contained upon or within the catheter or otherwise sufficiently compact to pass through the clot or other obstructive matter. Thereafter, the matter capturing receptacle is deployable (e.g., advanceable, projectable and/or expandable) from the catheter such that it assumes a second or expanded configuration wherein the receptacle may receive and at least partially surround the distal aspect of the clot or other obstructive matter so as to facilitate extraction and removal of the blood clot or other obstructive matter along with the catheter.
A guidewire lumen may extend longitudinally through the entire length of the catheter (i.e., an xe2x80x9cover-the-wirexe2x80x9d embodiment) or through only a distal portion of the catheter (i.e., a xe2x80x9crapid exchangexe2x80x9d embodiment). In either of these embodiments of the catheter, the guidewire lumen may extend through the matter capturing receptacle such that the catheter (with its matter capturing receptacle in its collapsed or stowed configuration) may be advanced over a guidewire which has previously been passed through the vessel-obstructing clot or other obstructive matter. Such arrangement of the guidewire lumen additionally allows the embolectomy catheter to be exchanged (e.g., removed and replaced with another embolectomy catheter or another type of catheter) if such exchange should become necessary or desirable. This ability to allow the guidewire to remain positioned through the offending clot or other obstructive matter may serve to ensure that the catheter or its replacement can be re-advanced through the clot or other obstructive matter to its desired position.
The matter capturing receptacle of the catheter may comprise a distal obstructive matter-engaging portion (e.g., a coil, basket or concave member) of porous construction (e.g., a woven, coiled or mesh structure formed of wire, fiber or fabric), which is attached to the catheter by way of one or more proximal struts (e.g. connector members (e.g., a plurality of thin wires or struts). Initially, with the matter capturing receptacle disposed in its first (e.g., collapsed or stowed) configuration, the distal end of the catheter is advanced through the clot or other obstructive matter. After the catheter has been advanced through the clot or other obstructive matter, the matter capturing receptacle is moved to its second (e.g., expanded or operative) configuration, such that the distal obstructive matter-engaging portion of the receptacle will contact and/or at least partially surround the distal aspect of the clot or other obstructive matter. The distal obstructive matter-engaging portion of the receptacle is preferably of permeable construction to permit blood to flow therethrough, but is sufficiently dense (i.e., sufficiently impermeable) to prevent the clot or other obstructive matter from passing therethrough. In this manner, the distal obstructive matter-engaging portion of the receptacle is useable to retract or draw the clot or other obstructive matter, in the proximal direction, from its then-present location. The proximal strut(s) which extend between the receptacle to the catheter are typically of radially splayed or outwardly angled configuration and is/are preferably configured, oriented and positioned so as to slice, cut or otherwise pass through the matter of the clot or other obstructive matter, when deployed at a site distal to the clot or other obstructive matter and subsequently retracted in the proximal direction. To assist such proximal strut(s) in passing through the clot or other obstructive matter, energy (e.g., radio-frequency energy, vibration, heat, etc) may be applied to the proximal strut(s) during their proximal retraction through the clot or other obstructive matter.
A contrast medium injection port may be formed on the proximal portion of the embolectomy catheter, to allow radiographic contrast medium (e.g., dye) to be injected through the catheter while a guidewire remains positioned within the guidewire lumen.
B. Rapid Exchange Microcatheter Useable in Conjunction with Embolectomy Catheters of the Present Invention
Further in accordance with the present invention, there is provided a rapid exchange microcatheter which comprises a small diameter flexible microcatheter of a type commonly used in neuroradiology procedures (e.g., Prowler(trademark) microcatheter, Cordis Endovascular Systems, Miami Lakes, Fla.), which has greater flexibility at or near its distal end than at or near its proximal end, and which includes in accordance with this invention, the addition of a guidewire passage port formed in the sidewall of the catheter, at a spaced distance (e.g., 0.5-35 cm) from its distal tip. A guidewire deflector may be formed within the main lumen of the catheter adjacent to the guidewire passage aperture, to deflect the proximal end of a guidewire out of the guidewire passage aperture as the catheter is advanced over the guidewire. The formation of such guidewire passage aperture and guidewire deflector allows a guidewire to be passed through only a distal portion of the catheter lumen. This lumen arrangement allows the microcatheter to be exchanged (i.e., removed and replaced by another microcatheter or an embolectomy catheter of the above-summarized design) while the operator holds the guidewire in place by grasping the exteriorized proximal end of the guidewirexe2x80x94even in instances where a standard length guidewire (i.e., not an xe2x80x9cexchange-lengthxe2x80x9d guidewire) is used.
C. Methods of the Present Invention for Removing Clots or Other Matter from Blood Vessels
The present invention also contemplates methods of removing clots or other obstructive matter from blood vessels. One method includes the use of a guidewire to first pierce and traverse at least portion of the clot to be removed. An embolectomy catheter of the present invention is advanced either with or over the guidewire and through the clot. A clot removal device provided on the catheter is then deployed radially outwardly, and the catheter retracted to entangle the clot removal device with the clot. Further retraction of the catheter in combination with optional suction removes the clot.
In a further method of the present invention, the guidewire includes an infusion lumen therein. After the guidewire is inserted through the clot, medication or clot dissolution fluid may be administered to the distal side of the clot. Alternatively, visualization fluid may be injected to obtain a better picture of the clot from the distal side thereof.
Further in accordance with the present invention, there are provided a method for treating ischemic stroke caused by a thromboembolism which has become lodged in a small blood vessel of the brain (i.e., blood vessels located in, on or around the brain). The method of the present invention may be carried out using the rapid-exchange microcatheters and embolectomy catheters of the present invention. An exemplary method generally comprises the steps of:
A. percutaneously inserting a guidewire (alone or in combination with a guide catheter) into an intracranial blood vessel, using the Seldinger technique or other appropriate method of percutaneous guidewire placement;
B. advancing a microcatheter over the guidewire, or separately from the guidewire, through the vasculature until the microcatheter is near the site at which the blood clot or other obstructive matter is located;
C. passing radiographic contrast medium (e.g., dye) through the microcatheter under radiographic visualization to verify the exact location of the obstructive matter and/or to map the vascular anatomy in the area of the obstruction;
D. advancing the guidewire (or a separate small guidewire) through the microcatheter until such guidewire becomes located in a desired operative position relative to the obstructive matter (e.g., such that its distal end has fully or partially traversed or passed through the thromboembolism or other obstructive matter);
E. withdrawing and removing the microcatheter while substantially maintaining the small guidewire in its operative position (e.g., preventing the guidewire from moving so far as to lose the access to the obstructive matter that the presence of the guidewire provides);
F. advancing a matter-capturing type embolectomy catheter (such as an embolectomy catheter of the present invention) which has an obstructive matter-capturing receptacle deployable therefrom, over the operatively positioned guidewire until the distal end of the embolectomy catheter has advanced fully or at least partially through the obstructive matter (e.g., has penetrated through an obstructive thromboembolism);
G. optionally injecting radiographic contrast medium through a lumen of the embolectomy catheter to guide or verify the positioning of the embolectomy catheter relative to the lodged blood clot or other obstructive matter;
H. deploying the obstructive matter-capturing receptacle of the embolectomy catheter such that it assumes its second or expanded configuration at a site which is distal (i.e., downstream) of the lodged blood clot or other obstructive matter;
I. retracting the obstructive matter-capturing receptacle such that a proximal portion of the receptacle (i.e., proximal struts) passes through the thromboembolism and at least a portion of the clot or other obstructive matter becomes located within the obstructive matter-receiving portion of the obstructive matter-capturing receptacle;
J. optionally injecting radiographic contrast medium through a lumen of the embolectomy catheter to determine whether blood flow has been restored through the region of the blood vessel which had previously been deprived of blood flow due to the presence of the clot or other obstructive matter; and,
K. retracting the embolectomy catheter to remove the blood clot or other obstructive matter from the body (e.g., withdrawing the embolectomy catheter and the extracted clot or other obstructive matter through the percutaneous entry tract through which the catheter had previously been inserted).
Thus, by the above-summarized method of the present invention, the blood clot or other obstructive matter which is causing an ischemic (i.e., thrombotic or embolic) stroke is removed and arterial blood flow is restored to the region of the brain which had become ischemic due to the lodging on the offending blood clot or other obstructive matter within the blood vessel.
D. Infusion Guidewire
An infusion guidewire of the present invention preferably comprises an inner wire and an outer sheath slideable thereover. The wire and sheath are first advanced together through the clot, and the inner wire is then retracted to open a lumen within the outer sheath. Advantageously, the outer sheath, or sheath and inner wire combination, can remain in place through the clot while different catheters are exchanged thereover.